The present invention relates to an automatic film sensitivity setting device for a camera and more, particularly, to a device for producing an electrical signal by utilization of the electrical contacts provided on a film patrone and delivering the signal to an exposure control circuit of an electronic shutter so that the proper exposure control is implemented.
Recently, a U.S. firm Eastman Kodak has commercialized the Camera Auto Sensing (CAS) system, in which the film patrone or cartridge is provided with six electrical contacts for providing 5-bit digital information relating to the film sensitivity. The inventor of the present invention has already proposed the method of entering the film sensitivity data to the camera by using these contacts. However, conventional systems need a D/A converter for transforming the 5-bit digital data into an analog signal, or a code conversion circuit in the case of a digital exposure control system, resulting in a complex and expensive circuit arrangement.
The above-mentioned CAS system allows the use of 24 kinds of film sensitivity indices ranging from 25 through 5000 in the ISO system. However, the film sensitivity available currently and used frequently in practice is less in variety.